This study investigates the association between individual differences in testosterone and communication after sexual activity. Two hundred and fifty-three young adult participants (78% women, M age = 21 years, 73% White) provided saliva samples (later assayed for testosterone) and subsequently, over a 2-week period, completed an online diary after each time they engaged in sexual activity. Individual differences in testosterone levels were inversely associated with perceived benefits of, and positively associated with perceived risks of, disclosing thoughts and feelings to one’s partner after sexual activity. When testosterone levels were higher, post sex disclosures were less intentional and less positive, and these associations were mediated by risk–benefit assessments. An interaction between testosterone and orgasm revealed that higher testosterone levels were associated with more negative post sex disclosures for those who did not orgasm, but not for those who experienced orgasm. This finding suggests that high testosterone/no orgasm individuals may be the least likely to experience the beneficial effects of post sex communication. Similar results were found both when biological sex was controlled for and when analyses were conducted separately for women and men. Implications for a biosocial model of post sex behavior and communication are discussed.